Coal processing oven and product recovery system



Aug. 25, 1964 v. MANsFlELD COAL PROCESSING OVEN ANO PRODUCT RECOVERY SYSTEM Filed June e, 1960 4 Sheets-Sheet J ATTORNEY Aug. 25, 1964 v. MANSFIELD COAL PROCESSING OVEN AND PRODUCT RECOVERY SYSTEM Filed June 6, 1960 4 Sheets-Sheet 2 O caws K @0005 N mw.

INVENTOR VAUGHN MANSFIELD ATTORNEY Aug. 25, 1964 v. MANsFlELD 3,146,175

COAL PROCESSING ovEN AND PRODUCT RECOVERY SYSTEM Filed June 6, 1960 4 Sheets-Sheet 5 STRIPPED FuEuAs 356 LIGHT FR COAL BURNER PRODUCT RECQVERY SYS TEM INVENTOR VAUGHN MANSFIE LD ATTORNEY Aug. 25, 1964 v. MANSFIELD COAL PROCESSING OVEN AND PRODUCT RECOVERY SYSTEM Filed June 6, 1960 4 Sheets-Sheet 4 l @mm .VDM Mmm m4@ JmDn- Duma- 1km mm INVENTOR VAUGHN MANSFIELD ATTORNEY United States Patent O 3,146,175 CUAL PROCESSING OVEN AND PRODUCT RECVERY SYSTEM Vaughn Mausiield, 301 Olive St., St. Louis, Mo. Filed .lune 6, 1960, Ser. No. 34,313 1 Claim. (Cl. 2in-22) This invention relates to a method and apparatus for continuous production of coke or char from coal or the like carbonaceous material while extracting therefrom and utilizing Volatile matter. This application is a continuation-in-part of my copending applications Serial No. 820,213 liled June 15, 1959, for Method and Apparatus for Continuous Coke Production While Extracting Low- 'Iemperature Volatiles, now U.S. Patent 3,013,951, and Serial No. 850,362, tiled November 2, 1959, for Char Producer and Distillate System for Non-Coking Coal, now abandoned.

The primary object of this invention is to provide for the processing of coal on a conveyer, such as a chain grate stoker, moving through an oven so as to drive off all but residual volatile matter and producing, as the end product of the iixed carbon, either coke or char, and extracting, as end products of the Volatile matter, tar and the lighter fractions. Although coking ovens of this general type, as exempliiied in the patent to Anderson et al., No. 2,209,255, have been operated from time to time for many years, one of the main problems has been to achieve sutiicient output with equipment of reasonable size and cost, and also to produce coke of suicient size and strength for metallurgical uses, and vto meet both conditions without burning excessive amounts of the iixed carbons in the coal. In prior operations it was deemed necessary to spread the coal to form a thin bed on the travelling grate because considerable time was required in order to raise the entire cross section of coal in a thick bed to plasticizing temperatures and above. If burning su'icient to raise the bed temperature quickly was permitted, many of the volatiles whose recovery was most desired, and also some of the fixed carbons, were burned. Of perhaps more concern was the tendency of the bed to channelize, either because of uneven distribution of the coal across or along the bed, or because of the natural tendency of the air sweeping through the bed to seek out paths of lesser resistance, the net result being that hot spots of intense burning would quickly form. The volatile matter and disproportionately large amounts of the xed carbons were consumed in the hot spots, while other portions of the coal within the bed received insufiicient heat. While preheating of the coal prior to its entry into the oven decreases the time necessary to heat the coal to coking temperatures within the oven, only limited external preheating could be accomplished lest the lowtemperature volatiles driven oit ignite and start premature burning in the bed. In raising temperatures in a thick bed from permissible preheat to plasticizing temperatures by passing air alone through the bed in quantities suicient to produce limited burning within the bed,

there still remained the problem of hot spot burning inV and adjacent the air channels formed through the coal bed.

The primary object of the invention is to provide a multi-stage coking process wherein the low-temperature volatiles are iirst removed from the coal with little or no burning of the volatiles, and wherein the coal throughout the entire width and thickness of the bed is first raised to plasticizing temperature, and then subsequently raised to higher temperatures in order to remove the high-temperature volatiles. In its broadest aspects, the invention contemplates the segregation of a coking oven into diS` crete contiguous zones wherein diierent functions of coking or charring procedures are sequentially performed ICC as a continuous bed of carbonizable material, such as coal, progresses through several discrete zones.

According to one embodiment of the invention, disclosed in Serial No. 820,213, preheated coal is passed into a low-temperature devolatilizing discrete zone and small quantities of preheated air and recycle gas are fed through the coal in order to raise the bed temperature to a degree at which the entire bed becomes plastic. As the coal approaches and reaches plasticizing temperatures, the low-temperature Volatile matter is removed and fed to a product recovery system wherein the tars and lighter oils are removed, and part of the remaining fuel gas is stripped off heated and recycled through the coal in the devolatilizing zone. If coke is to be formed, the coal is next passed into a contiguous high-temperature zone, wherein the bed temperature is raised suiliciently to drive oli most of the high-temperature volatile matter and to set the coke into large strong lumps. The high-temperature heating of the bed is accomplished by feeding preheated air through the bed in sufficient quantities to permit limited combustion of the high-temperature volatiles, and by feeding over-fire air over the bed to create a fireball for raising the zone temperature and for radiantly heating the coal in the bed. Also, as the coal passes through the high-temperature oven zone, hot stack gas may be fed through the bed, along with the preheated air, in order to sweep the high-temperature volatiles oli? from the bed and into the fireball. Subsequently, the coke is discharged into a cooker, wherein residual hightemperature volatiles are driven off, and wherein the coke is subsequently quenched.

According to other embodiments of the invention, newly disclosed herein, the coal, either preheated or raw, is iirst passed through a discrete oven zone wherein hot spent gases are downdrafted through the bed as it progresses therethrough so as to raise the bed temperature nearly to the degree at which the coal starts to become plastic, the coal next passing into a black furnace zone wherein the coal, without combustion, reaches plasticizing temperature and the low-temperature volatiles are removed. If coke is to be produced, the plasticized coal then passes into a combustion zone wherein the hightemperature volatiles are driven oi and the coke is set; but, if char is to be produced, the black-furnace treatment is extended, the combustion zone is eliminated, and the char is subjected to iinal heating in a cooker associated with the output end of the oven.

These and other objects will be apparent from the following specication and drawings, in which:

FIG. l is a diagrammatic vertical section taken longitudinally through the center of apparatus constructed according to one form of the invention;

FIG. 2 is a View similar to FIG. 1, but illustrating a second embodiment of the invention;

FIG. 3 is a view similar to FIGS. l and 2, but illustrating a third embodiment of the invention; and,

FIG. 4 illustrates a modification of the FIG. 3 system.

Referring now to the drawings, in which like reference numerals denote similar elements, FIG. l illustrates the system disclosed and claimed in Serial No. 820,213. The iiow circuits for the process and apparatus will iirst be described so that the inter-relationships of the components of the system may be understood and correlated in the description of the details.

Bituminous coal is fed from a supply bin 10 through a suitable chute or conveyer 11 to a preheater 12 in which the coal is brought up to a temperature of about 350 F. to 450 F. The coal should be preheated up to, but not including, the temperature at which the coal starts to kgive olf appreciable volatile matter, this temperature depending on the particular coal being used. From preheater 12 the coal, which, after preheating, is

substantially moisture free, is introduced through the chute or other suitable conveyer 13 to an input hopper 14 having at its outlet end an igniter 16, which may be gas fired or electrically heated, the ignited coal then being evenly distributed by a spreader gate 17 on a travelling grate 18, on which the ignited-bed 19 of coal travels through a coking oven 2G. In passing beneath the front zone 21 of the oven, wherein the oven roof 22 is low, the low-temperature volatiles (those which are driven off in the temperature range between 848 F. to 1060 F.) are removed from the coal and, as the bed passes through the rear portion 23 of the oven having a raised roof 22a, most of the high-temperature volatiles (those which are driven off at `bed temperatures between 1060 F. and 1800 F., or 1900 F.) are removed. As the bed reaches the rear end of travelling grate 18, it passes beneath a hot gas outlet 24 which supplies heat to a boiler or the like heat utilizing device (not shown) and is then discharged into a quenching retort 26 which lies beneath the rear end 28 of coking oven 20. The residual volatiles, in the range of 4% to 8% of those originally in the coal, which remain in the then nearly completely carbonized product are driven off, in retort 26, by the latent heat in the coke as the coke stack moves through the upper portion 99 of retort 26, and the coke is quenched in the lower portion 100 of the retort and then discharged by a feeder 30 onto a conveyer 32, the coke then having been quenched to below its ignition temperature.

The low-temperature volatiles removed from the coal as it passes through zone 21 are extracted through an outlet 34 and fed through a suitable conduit 36 to a product recovery unit 38, wherein the low-temperature volatiles are distilled and scrubbed, and taken off as light oil, medium oil and pitch through conventional outlets indicated, as a group, at 40. The fuel gas output of product recovery system 38 is discharged through line 42, a portion of the fuel gas output being fed by a line 44 to a suitable utilization device, which may include igniter 16. The remainder of the fuel gas output of product recovery system 38 is fed through a branch 46 and pump 48 to a heat exchanger 50, wherein it is heated and thence passed through a supply line 52 to a fuel gas manifold 54, from which it is recycled by fuel gas lines, one of which is designated FG to the rst four zones of an air box 56 which extends beneath the length of travelling grate 18. The feed of fuel gas from manifold 54 to each of zones 1 to 4, inclusive, is individually controlled by valves, one of which is indicated at 58. Part of the fuel gas output of product recovery system 38 is thus used to sweep otf the low-temperature volatiles, and to maintain carbonizing temperature in the coal bed as the latter passes over the first four Zones of air box 56, these rst four zones lying beneath zone 21 previously designated.

Primary air is supplied through an intake line 60 and thence forced by pump 62 through an air preheater 64. Part of the preheated air is supplied by a line 66 to a preheated air manifold 68, from which the primary air is distributed by individual air lines, one of which is designated AL to all eight zones of the air box 56, the air feed to the separate Zones being individually controlled by valves, one being designated 70. The remainder of the preheated primary air is taken off line 66 through a branch line 67 and thence fed through control valves 70 to over-tire air ports 71 which enter the oven in zone 23 beneath the roof 23a of the high-temperature section of the coking oven.

Part of the stack gas from furnace 24 is taken olf and circulated through coal preheater 12 via supply and re turn lines 72 and 74, respectively, a pump 76 being provided to force the circulation. Some of the other stack gas is taken otf via supply line 78 and forced by pump 82 to stack gas manifold 84, and thence distributed by individual supply lines, one of which is designated SG to the last four zones of air box 56, the supply of stack gas to the separate zones being individually controlled by valves, one being designated 85. A portion of the stack gas is taken ott line 80 via branch 88 and thence, through valve 90, into a line 92, in which it is forced by pump 94 to a manifold 96 surrounding the lower part of a quenching retort 26. From manifold 96, cool stack gas, which is substantially inert, passes through ports 98 into the lower portion of the coke stacked in the retort. The stack gas entering ports 9S creates a pressure, sufficiently above atmospheric pressure, to prevent air from entering upwardly through discharge opening 31 at the bottom of retort 26, a small portion of the stack gas leaking outwardly past feeder 30. Most of the stack gases entering ports 98 pass upwardly through the stack of coke in the lower portion 100 of retort 26, and most of the upwardly owing stack gases then flow outwardly through ports 102, manifold 104 and through return lines 106 and 106:1 and valve 107 to heat exchanger 50 and air preheater 64, which is also a heat exchanger. Heat in the lower portion of .the coke stack in retort 26 transfers to the stack gas and is transmitted thereby to heat exchanger 50 and air preheater 64, wherein a large part of the heat is given up to the fuel gas and primary air which tlow through heat exchanger 50 and air preheater 64.

A small portion of the stack gas flowing upwardly through the lower portion of the coke stack in retort 26 does not emit via ports 102 but, rather, passes on upwardly through the hot unquenched coke in the upper portion 99 of the coke stack in retort 26 so as to sweep otf the residual volatiles which are driven olf by the latent heat in the coke in the upper portion 99 of the stack, these volatiles then being consumed in the fire ball 116 described hereinbelow.

Returning now to the entry of the ignited preheated coal into coking oven 20, spreader gate 17 is adjusted to provide a relatively thick but uniformly distributed bed 19 of coal on travelling grate 18. One feature of the invention is that relatively small coal, even 1A" by 0, may be used to form coke agglomerate. The travelling grate is driven by a suitable source of power, not shown, it being understood that the grate, which may be of chain or perforate sections, moves the bed slowly from left to right, as seen in the drawing. In a typical embodiment, the upper run of the grate is from twenty to thirty feet long and from twenty to thirty feet wide. Spreader gate 17 is adjusted, by control mechanism 108, to provide a comparatively thick bed, in the range of four to twenty inches in depth. The maximum height of roof 22 should be about thirty-six inches above the grate. Preheating of the coal has been found desirable so as to avoid the necessity of extensive ignition, to provide for ready ignition of the entire bed from top to bottom, to eliminate moisture and so that only a small amount of primary air need be fed upwardly from zone 1 of air box 56 to firmly start and maintain carbonization through the bed. Without preheating of the coal, so much primary air must be fed up from zone 1 to ignite the bed that excessive combustion of the lowtemperature volatiles takes place. This results in dilution of the low-temperature volatiles by the CO2 combustion product and nitrogen.

In starting the process, enough primary air is fed upwardly from air box zones 1 to 8 to bring the oven up to its operating temperatures. Thereafter, the air valves 70 for air box zones 2 to 4, inclusive, are closed, or barely cracked, while the air valve 70 for zone 1 is opened so as to supply enough primary air to completely ignite bed 19 from top to bottom. However, the primary air supply is limited so that the bed temperature does not exceed 1060 F. as it passes above air box zones 1 to 4.

Fuel gas valves 58 are adjusted so as to feed fuel gas to zones 2, 3 and 4 of air box 56 so as to sweep otf the low-temperature volatiles. It will be understood that bed 19 is initially partly ignited as it enters oven 20 and ignition is completed by forcing air upwardly through it as the bed passes over the first zone, and it remains ignited as it passes over zones 2, 3 and 4. Assuming that the coal input to the oven had about 40% volatile content, approximately 58% of the original volatiles will have been driven off by the time the bed progresses beyond partition 110. Partition 110, is of course, adjusted by mechanism 112 so that the top of the bed scrapes along its lower edge. The low-temperature volatiles, including the tars, which are driven off the coal as the bed 19 passes over air box zones 1 to 4, inclusive, are exhausted through outlet 34 as previously outlined.

Air valve 70 leading to air box zone 5 is adjusted so that substantially more air is fed upwardly through bed 19 over zone 5 than was fed up from zone 1, and the air valves for zones 6, 7 and 8 are closed, or barely cracked. The rate of carbonization, when bed 19 passes above zone 5, is sharply increased so that the bed reaches temperatures in the range of 1800 F. to 1900 F. The stack gas feed to zones 6, 7 and 8 is adjusted so as to sweep off the high-temperature volatiles. However, over zones 5, 6, 7 and 8, the bed temperatures are not created solely by combustion within the bed. The unburned high-temperature volatiles, after being swept upwardly through the bed, combine with over-lire air fed in through ports 71 and ignite, thereby creating a lire ball in the region indicated generally at 116. The radiant heat from re ball 116 progressively raises the temperature of the bed, from the top downwardly, as the bed progresses over air box zones 5, 6, 7 and 8.

The speed `of movement of bed 19 from left to right, as seen in the drawing, is maintained so that by the time the bed passes beyond rair box zone 8 and thence ot the end of the travelling grate, most of the high-temperature volatiles will have been driven olf. However, the bed is moved suficiently fast so that the high temperatures developed by the radiant heat in passing over the last four Iair box zones will not have completely worked down to the surface of the grate. By leaving residual volatiles in the nearly completely carbonized bed, excessively high temperatures on the grate surface are avoided and thus longer grate life is achieved. In addition, considerably more tonnage can be handled on the grate by moving a thick bed through the coking oven at a rate faster than that which would achieve more complete carbonization, wherein the bed would be retained on the grate for la longer time, and higher temperatures would be developed on the grate surface. However, the bulk of the bed will, iat the time it passes over the end 4of the travelling grate, have developed sufficiently high temperatures so that by co-mingling the nearly completely carbonized coke in the upper portion of retort 26, the residual volatiles will be driven off by the latent heat within the bed.

After preheating the oven, sufficient coke is run through to lill retort 26 nearly to its top, and thereafter feeder 30 is operated to discharge coke on the conveyor 32 at the same rate that the nearly completely carbonized coke is dumped olf travelling grate 18 into the top of retort 26. For purposes of demonstrating the operation of the system, the stack gas has been considered as virtually inert. Actually, a small amount of oxygen remains in the gas as it is derived from the stack. If desired, the oxygen content may be removed by conventional apparatus. Sullicient `stack gas is fed through line 78, valve 90 and line 92 so that, upon operation of pump 94, stack gas is circulated into retort 26 through manifold 96, ports 98 and thence upwardly through the lower portion 100 of the coke in retort 26, and thence out ports 102, manifold 104 and lines 106 and 106a through heat exchanger 50 and preheater 64. When the circui-t through heat exchanger 50, air preheater 64 and the lower portion 100 of retort 26 is charged with stack gas, only enough additional stack gas need be introduced through valve 90 to make up the losses resulting from downwardly escaping gas through feeder 30, and the upward flow of stack gas through the upper portion 99 of retort 26, the last mentioned flow being sulicient only to sweep olf the residual volatiles which are driven from the coke as a result of the latent heat remaining as the coke is dumped off the end of the travelling grate. The high-temperature volatiles swept oil the coke in the upper portion 99 co-mingle wi-th those swept upwardly from the portion of the bed travelling over air box zones 5, 6, 7 and 8 and are consumed in fire ball 116.

The heat extracted from the coke in the lower portion 100 of retort 26 by the up-lowing stack gases is transferred in heat exchanger 50 and air preheater 64 to the fuel gas owing into manifold 52 and the primary air for manifold 68 and, in turn, the heat is fed back to bed 19. It is contemplated that the coke at the top of the upper portion 99 of retort 26 will be at approximately 17007 F.; the stack gases leaving retort 26 through ports 102 will be at :approximately l500 F.; and the stack gases entering the retort through ports 98 will be at approximately 200 F.

The relatively high coking temperatures achieved in the bed at the end of travelling grate 18 and at the top of retort 26 results in an extremely strong coke agglomerate, particularly adapted for metallurgical sintering and as a chemical agent in chemical processes, such as in the production `of carbide and elemental phosphorus. The products derived from recovery system 38 have widespread use; and the heat output through outlet 24 is usable in an :adjacent boiler or the like heat utilizing device.

Reference is now made to FIG. 2 of the drawings, wherein a second embodiment of the invention is diagrammatically illustrated. A horizontally elongate coke oven 103 is formed of ceramic or heat resistant material, and chain grate stoker 105 is conventionally mounted in the oven, with its upper `or load-carrying run 107 moving horizontally through the oven from a hopper 109 adjacent the oven input end 111 to the oven output end denoted generally at 113. A zoned airbox 115 is disposed between the upper run 107 and the lower run 117 of the stoken and between the 4sprockets 119 and 1'21 over which the runs turn at the end, the sprockets being conventionally driven by a suitable torque source. Airbox 115 is divided into separate zones, twelve being shown for the present examples, lettered a to l. The mechanical details of a zoned airbox operating in conjunction with a chain grate stoker are well known in the art, it being suffcient to note that the air or gas flowing to or from the material carried on any given part of the upper run of the grate is controlled primarily by the airbox zone disposed immediately below. Disposed below the output end 113 of oven 103 is a coker-quencher retort or cooker 123, into which the coke drops from the end of the upper grate run. After seasoning and cooling in cooker 123, the coke is removed from the lower end through a substantially airtight discharge mechanism, one of several types being illustrated at 125.

Returning to the input end of oven 103, coal is sup-` plied through hopper 109 and spread to form a thick bed, in the range of 6" to 12" in depth, over grate run 107 by a spreader gate 127 whose height may be varied by conventional adjusting mechanism 129.

As it enters the input end of the oven, the coal passes through a preheating zone 131, overlying the rst two zones a and b of airbox 115, wherein hot spent gases are downdrafted through the bed, as later detailed. Next to preheating zone 131 is a black furnace zone 133, so called because no appreciable combustion occurs therein, even though the temperature would be suflciently high to ignite the coal if suflicient air were present. Black furnace zone 133 is discrete, i.e., is separated from the adjacent zones by a spaced pair of curtain walls 135 and 137, respectively, each having a sealing shoe 139 along its lower edge for riding on and sealing against the top of the coal layer carried on the grate. The curtain walls are preferably vertically movable by adjusting mechanism diagrammatically shown'at 141. From black furnace zone 133, the coal, having been stripped of its low-temperature volatile matter, passes into a carbonization zone 143, wherein sufficient air is supplied to permit limited burning, and to raise the bed ternperature from approximately 1000 F., which it attained in black furnace Zone 133, to 1800 F., thereby driving off and burning practically all of the high-temperature volatile matter remaining. It will be observed from the FIG. 2 diagram that the portion 145 of top of the oven over the preheating zone 131 is raised so as to provide ample volume for complete distribution of the incoming preheating gases; the oven top 147 over the black furnace zone 133 may be relatively low; and the oven to portion 149 over the carbonization zone 143 wherein burning occurs is relatively high so as to provide increased Volume in the zone of extensive heat release.

The heat, gas and air systems for the FIG. 2 embodiment are as follows: associated with oven 103 is a product recovery system 151, in which tar, the lighter fractions, and stripped gas are separated and recovered from the make gas fed to system 151 by conduit 153 leading from an outlet 155 from black furnace zone 133. Part of the stripped gas derived from system 151 by a gas line 157 is fed through a branch line 159 for burning, as fuel, in a gas heater 161, a Valve 153 controlling the fuel gas input to the heater. The spent gas, virtually oxygen-free and at approximately 800 F., are exhausted from -gas heater 161 through a line 165 and inlet 167 into the top of preheating zone, those hot spent gases then being drawn downwardly into airbox zones a and b, and thence through pipes 169 and 171, control valves 173 and 175 and pump 177 to an exhaust line 179. As the temperature of the coal passing through preheating zone 131 rises from room temperature (assuming no external preheating has occurred) to approximately 650 F., some of the-low-ternperature volatiles will be driven off and swept away, along with the original moisture, by the hot spent gases. However, the transit time of the coal bed through the preheating zone is sufficiently short so that the coal does not attain temperature sufficient to drive off any but a small portion of the low-tempera ture volatiles until about the time it passes beyond the preheating zone, and thus only a comparative few volatiles are sacrificed.

Part of the stripped gas at` 100 F. output of recovery system 151 is fed via line 1251, controlled by valve 183, through gas heater 161 wherein its temperature is raised to approximately 1200 F., the gas being forced through a supply line 185 by a pump 187 into stripped gas manifold 189. Pipes 171, controlled by valvesi193 feed the hot stripped gas to airbox zones c and f, inclusive, beneath black furnace zone 133. In passing upwardly through the coal bed on the grate, the hot gases maintain the coal at approximately 1000D F. and, during the transit time of the coal through zone 133, most of the low-temperature volatiles are driven oii by the heat and swept off by the flowing gases, and fed to recovery system 64 as previously detailed. By utilizing hot stripped gas devoid of oxygen, combustion within or above the bed is avoided as the coal passes through zone 133, and the preheating zone 131, being at below atmospheric pressure, serves as a sealing chamber to prevent escape of the hot stripped gas to the atmosphere.

For feeding hot air upwardly through the coal as it passes through carbonization zone 143, there is a manifold 195 connected by pipes 197 to airbox zones g to l, inclusive. Control valves 199 in the pipes provide selective feed to the airbox zones, and a pipe 201 having a control valve 203 leads to ports 205 adjacent the lower end of a stack 207 for supplying over-fire air so that a fireball may be created over the bed in combustion zone 143 if desired. Heat for the air fed to manifold is extracted from the hot coke as it passes downwardly through the lower end of cooker 123, there being a circuit 209 for inert gas extracted by the ports, one of which is shown at 211, intermediate the upper and lower ends of the cooker.y

through a heat exchanger 215 wherein it gives up heat, and back through ports 217 into the coke in the lower end of the cooker. Inert gas, such as spenttiue gas issuing from a heat utilizing device (not shown) supplied by stack 207 may be used for supplying and making up the gas for circuit 209. Air drawn from supply line 219 is forced by apump 221 through the heat exchanger and fed, at approximately 900 F. through line 223 to manifold 195. In a typical operation, Belleville` coal, size 1A" x 0 is utilized as the starting material, the original constituents being approximately as follows:

Moisture 10.94%.

Ash 9.71% 10.90% dry basis. Volatiles 35.79% 40.19% dry basis. Fixed carbon 43.56% 48.91% dry basis.

After traversing preheating zone 131, the moisture content is approximately zero, and it is estimated that the volatile content is between 39% and 40.19% of the dry coal, the temperature of all the coal in the bed, as it passes beneath shoe 139 on curtain wall 135 is approximately 650 F. The fixed carbon content is then the same quantity as at starting, but is now 48.91% of the dry coal, and the ash being 10.90%.

After traversing black furnace Zone 133, the volatile content of the char or coke in the bed is estimated at 12.05%, the fixed carbons remaining in the same quantity, but now comprising 71.92% of the char or coke, and the ash being 16.03%. The temperature of the bed, as it passes beneath curtain 50 is approximately 1000 F., the char or coke being ready as air is fed through it, to

become more completely devolatilized as soon as the bed,

temperature reaches approximately 1800 F.

As the coal passes into carbonization zone 143, the hot air fed through the bed from airbox zones g and lz ignites the coke sufficiently to raise the bed temperature to approximately 1800 F., thereby driving off and partly burning some of the high-temperature volatiles, and firmly coking from bottom to top. By thus eliminating the low-temperature volatile matter, and by raising the entire width and thickness of the bed up to plasticizing temperature, hot spots of localized burning are avoided. Furthermore, by avoiding conditions under 'which a zone of plasticity extends diagonally downward through the bed, from the input end of the furnace nearly to the output end of the grate run, as prevailed in prior practices, piecemeal setting of the coke is avoided, and the entire vertical cross-section of the coke being formed in the bed sets almost simultaneously. The high-temperature volatiles which are driven off, but which do not burn in the bed, because of insufficient air fed through airbox zones g and l1, pass upwardly towards stack 207, and burn with the overfire air fed in through ports 205, thereby creating a fireball. Air in decreasing amounts is fed upwardly through airbox zones i, j, k and l, sufficient only to permit burning of all but residual amounts estimated at 2% to 3%, of the remaining high-temperature volatiles and a small portion of the fixed carbon, the setting of the coke being further enhanced. By the time the coke drops ofi the end of the upper grate run, its temperature should then be approximately 1800 F., the fixed carbon content about 78.58%, ash about 19.42%, and residual volatiles about 2.0% to 3%.

In the upper portion of cooker 123, the heat drives off virtually all of the residual volatiles, these passing upwardly and being consumed in the fireball. After quenching in the lower part of cooker 123, the coke, then being in large strong `lumps, consisting of approxi- The hot gas in circuit 209 is withdrawn from ports 211.by a pump 213, forced` mately 78.58% xed carbon, 19.42% ash and 2.0% residual volatiles, is discharged at approximately 200 F.

Referring now to FIGS. 3 and 4 of the drawings, the basic principle of the FIG. 1 embodiment is utilized in that the coal is treated in discrete low and high temperature zones of a coking oven as it passes horizontally through on a conveyer, and the improvement of the FIG. 2 embodiment is utilized in that the coal is rst heated nearly to plasticizing temperature by downdrafting hot spent gases through it in one discrete oven zone and then raised to plasticizing temperature in an adjacent discrete oven zone. However, in the FIG. 3 and FIG. 4 embodiments, char is produced in the oven and the coal is finally devolatilized in the cooker by subjecting it to ncreased temperature and time.

In FIG. 3, the char producing oven 302 has a chain grate stoker 304 whose upper load carrying run carries Coal from a hopper 308 adjacent the input end of the oven 310 to the output end 312. An airbox 314 having zones a to l, inclusive, as disposed between the upper and lower grate runs 306, 316, and between the sprockets 318 and 320 over which the ends of the runs are driven yby a suitable torque source. The treated coal, then charred, drops olf the output end of the upper grate run into a cooker 322 through which it progresses downwardly-to a suitable air-sealed discharge, such as screw conveyer 324. As the char passes downwardly through the upper portions of cooker 322, residual volatile matter is driven olf and, as it passes through the lower part of the cooker, it is quenched sufficiently so that it may be handled in the open without catching fire.

Bunker coal at about 60 F. fed into hopper 308 is rst spread evenly across upper grate run 306 by a spreader gate 326 whose height may be adjusted by conventional mechanism diagrammatically indicated at 328 to form a bed of uniform depth from 6" to l2". Next beyond spreader gate 326, the coal passes through a preheating zone 330, wherein hot spent gases are downdrafted through the bed. Next adjacent preheating zone 330 is a black furnace zone 332 separated from the preheating zone by a curtain wall 334 having a sealing shoe 336 along its lower edge which-rides on the top of the bed so as to prevent significant gaseous intercourse between the adjacent zones, the height of curtain wall 334 being variable so as to accommodate it to the selected bed thickness by conventional adjusting mechanism 338. As contrasted with the corresponding zone of the FIG. 2 embodiment, black furnace zone 332 is much longer, occupying the entire rear end of the oven, and the oven roof 339 may be relatively low, since no significant heat release occurs therein.

As the char drops off the end of the grate run into a iinal devolatilizing zone 340 in the upper portion of cooker 322, it rst passes through a throat 342 connecting the output end of oven 302 with the upper end of cooker 322, the char stacked in the throat providing a choke which limits gaseous flow between the cooker and the oven. Laterally of throat 342, and separated therefrom by a partition 345 is a combustion zone 346 in which burns the flame from a gas burner 382, the heat from which drives olf and burns with the high-temperature volatiles then remaining in the char.

The gas system for the FIG. 3 embodiment is as follows: leading from an outlet 348 is a gas line 350 through which the volatile matter driven and swept from the coal as it passes through black furnace zone 332 passes at about l000 F. to a product recovery system 352. The details of system 352 are not relevant here, it being sufficient to note that tar and lighter fractions are recovered from the volatile matter, and also fuel gas is stripped out and passed through a line 354 and propelled by a fan 356 through a line 358, controlled by valve 360 to a manifold 362 which connects via ports 364 to the lower end of cooker 322. The fuel gas entering ports 364 at about 100 F. passes upwardly through the lower end of cooker and exhausts through ports 366 and manifold 367 to an outlet line 368. In transit through the lower end of the cooker, the fuel gas absorbs heat from the char, thereby cooling the latter down from about l650 F. to 200 F., and thereby also raising the temperature of the gas to about 900 F. A fan 370 propels the heated fuel gas to a supply line 372. Also leading to supply line 372 is a fuel gas bypass line 374 leading from the high-pressure side of fan 356. A fuel gas take-olf branch 376 controlled by valve 378 leads from a supply line 372 to a gas utilizing device, such as a gas tired rotary kiln. j

Leading from fuel gas bypass line 374 is a burner supply line 380 which feeds cool fuel gas to burner 382, a Valve 384 controlling the burner gas supply, and air ports 386 provide the combustion air for the gas burner.

The hot spent gases, starting at about 2000 F. pass upwardly from combustion zone 346 through a stack 388 to a heat exchanger 390. A heat-sensing device 392 in the throat 393 leading into heat exchanger 390 has a control 394 for a valve 396 in a branch line 398 leading from exhaust fan 404 into stack 388 for tempering the gas supplied Vto the heat exchanger. Gas at about F. from bypass line 374 is blended in supply line 372 with the gas at about 900 F. from outlet line 368 so that the resultant mixture in supply line 372 is at about 282 F. The quantity of the spent gas entering heat exchanger is controlled by a damper 400 in a bleeder duct 402 which leads to an exhaust fan 404 and thence to an exhaust outlet 406.

The somewhat cooled, spent, and substantially inert gas from heat exchanger 390 at about 800 F. passes through a heat exchanger outlet 408 and through an inlet 410 into pre-heating zone 330, wherein they are downdrafted through the coal on grate run 306 and into airbox zones a and b, and thence through outlet pipes 412 contr'olled by valves 414 to an exhaust line 416 which leads to exhaust fan 404. The amount of gas fed to preheating zone 330 may also be controlled by a damper 400:1 in bleeder branch 402:1 leading to bleeder duct 402.

Airbox zones c through l are supplied with fuel gas as follows: connected to fuel gas supply line are heat exchanger coils 418, in passing through which the fuel gas extracts su'cient heat from the 1800 F. spent gas to raise the fuel gas temperature to about 1200 F., the latter then flowing through line 420 into a manifold 422 and thence through pipes 424, controlled by valves 426, into airbox zones c through l.

The elfect of the above ltreatments on the coal is as follows: in describing a typical operation of the FIG. 3 embodiment, it will be assumed that the starting material is Western Kentucky #11 Seam coal, 1A by 0 size approximately the following constituents:

Percent Moisture 8.73 Ash 5.47

Volatiles 39.12

Fixed carbon 46.68

Ash 5.47% dry basis.

Volatiles 39.12% dry basis.

Fixed carbon 46.68% dry basis.

As the preheated coal passes through black furnace zone 332, the hot fuel gas at approximately 1200 F. fed upwardly through the bed drives oif most of the volatile matter which can be liberated at temperatures up to about 1000 F., and sweeps the liberated volatiles to and through outlet 348. As the nearly carbonized coal reaches the 1 1 output end of the grate run at a temperature of about 1000 F., its constituents are estimated as follows:

Percent Ash 10.94 Volatiles 2.0 Fixed carbon 87.06

In devolatilizing zone 340 of cooker 322, the heat from gas burner 382 raises the temperature of the exposed char Ito .about 1650" F. thereby liberating and burning off virtually all of the residual volatiles so that the constituents of the resultantchar quenched in the lower end of cooker 322 are primarily fixed carbons and ash.

The embodiment illustrated in FIG. 4 is similar in most major respects to that disclosed in FIG. 3, the elements corresponding directly to those previously detailed being designated with similarV ordinary numerals, and those corresponding functionally being designated with prime numerals.

The main differences in the FIG. 4'embodirnent relate to the preheating and drying of the coal. Across the outlet conduit 408 of heat exchanger 390 is disposed a step louver 409. Coal from a bunker 411, controlled by a turnstile 413 in coal input throat 415 slides along louver 409 and inso doing is wiped by the hot gases issuing at about 800 F. from heat exchanger 390. The hot gases, carrying oil all moisture from the coal, are discharged via line 417 leading to exhaust fan 404 and the temperature of the coal is raised from an initial 60 F. to about 350 F. The dry and partly preheated coal then feeds to a closed hopper308 and thence on conveyor run 306 into preheating zone 330'.

In passing through preheating zone 330', the temperature of the coal is raised to about 650 F. by heat supplied by an igniting hood 419 in which burns a gas burner 421 supplied with fuel gas from outlet 354 via line 423. Only suicient air is supplied to burner 421 through a valve controlled air line 425 to burn with the gas, and thus there is no appreciable oxidation of the coal as it passes through preheating zone 330.

The basic principle underlying all embodiments of the invention are: the stepwise temperature treatment of the coal as it passes through the ovens; the segregation of the ovens into discrete zones wherein the treatments of the coal under relatively low and high temperature conditions in the adjacent discrete zones do not interfere with one another; the elimination of the comparatively lowtemperature volatiles before the coal is subjected to higher temperature treatment; the preheating of the coal to ternperatures approaching those at which the bed starts to plasticize; and the subsequent quick raising of the coal temperature throughout the entire depth of the bed, either to coking or charring temperatures.

The invention is not limited to the details shown and described herein, but is intended to cover all substitutions, modifications and equivalents within the scope of the following claim.

I claim:

The method of producing coke and gas from carbonizable coal which contains low temperature volatiles capable of being driven off at temperatures of a certain degree and below and high temperature volatiles capable of being driven off at carbonizing temperatures above said certain degree, comprising: transporting a substantially uniformly thick horizontal bed progressively through a series of discrete contiguous regions of a confined horizontally elongate space, partly devolatilizing the coal by progressively raising the temperature of the coal to said certain degree as the coal progresses from region to region, extracting from at least one of said regions the low temperature volatiles driven from the coal as the latter progresses therethrough, stripping fuel gas from the extracted i low temperature volaties, forming a stack of the partly devolatilized coal by dropping the latter olf the end of the bed into a vertically elongate confined space contiguous at its top with the horizontally elongate confined space, burning part of the stripped fuel gas over the top of the stack and radiantly heating the coal to carbonizing temperature as the latter falls onto the top of the stack, and maintaining the coal in the stack until most of the high temperaturevolatiles are liberated therefrom while removing the carbonized coal from the bottom of the stack.

References Cited in the le of this patent UNITED STATES PATENTS 1,591,023 Ditto et al. July 6, 1926 1,639,356 Wallace Aug. 16, 1927 1,814,463 Trent July 14, 1931 1,839,741 Davies Ian. 5, 1932 2,131,702 Berry Sept. 27, 1938 2,209,255 Anderson et al. July 23, 1940 2,380,930 Anderson et al Aug. 7, 1945 l2,668,760 Breyer et al. Feb. 9, 1954 2,710,828 Scott June 14, 1955 3,013,951 Mansfield Dec. 19, 1961 FOREIGN PATENTS 188,693 Great Britain Nov. 20, 1922 

